FA-75712 / Text diff and three-way merge / Member archive

Patch reversal: header starts are swapped but counts are not · case 02

The reversed hunk's header counts disagree with its body.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Reverse one unified hunk: swap the old and new ranges in the header, keeping each range's count omitted if it was omitted and keeping any trailing header text; swap "-" and "+" on body lines; within each run of changed lines emit the (new) removed lines before the (new) added lines; a "\" marker line stays attached to the line it follows.

Why this case matters

Reverting a change applies the reversed patch, which must still be a valid, conventionally ordered hunk.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
explicit zero count	`["@@ -1,0 +0,2 @@", "-n0", "-n1"]`	`["@@ -1,2 +0,0 @@", "-n0", "-n1"]`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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